Channel multiplier assembly and method of manufacture thereof

ABSTRACT

A bundle of individual channel multipliers stacked to form a multiplier array, the individual channels being fabricated of a lower temperature softening glass and the bundle being inserted into a higher temperature softening glass tube, the walls of the individual channels being expanded to fill the interstices within the higher softening temperature tube.

Elite Sates t [151 3,6 Cross et al. [451 Jufly 18, 1972 [54] CHANNEL MULTIPLIER ASSENmLY 3,407,324 10/1968 Rome ..3l3/l05 x AND METHOD or MANUFACTURE THEREOF FOREIGN PATENTS OR APPLICATIONS 1,064,072 4/ l 967 Great Britain Primary ExaminerBenjamin A. Borchelt Assistant Examiner-N. Moskowitz Anomey-Plante, Hartz, Smith and Thompson and William F. Thornton [57] ABSTRACT A bundle of individual channel multipliers stacked to form a multiplier array, the individual channels being fabricated of a lower temperature softening glass and the bundle being inserted into a higher temperature softening glass tube, the walls of the individual channels being expanded to fill the interstices within the higher softening temperature tube.

2 Claim, 6 Drawing Figures CHANNEL MULTIPLIER ASSEMBLY AND METHOD OF MANUFACTURE THEREOF BACKGROUND AND SUMMARY OF THE INVENTION This invention relates generally to a channel multiplier array and a method of producing the array, and more particularly to a method of expanding the individual channels within an outer glass jacket to fill the interstices between the individual channels and between the channels and the outer tube and the resulting apparatus.

Early uses of electron multipliers involved the provision of a plurality of individual glass channels formed of straightthrough tubes, the individual channels being stacked in a bundle to form an array. This array was utilized, for example, to multiply the number of electrons introduced at the input end of the channel multiplier array by means of secondary emission of electrons from the interior surface of the channels. Thus, an electron introduced into one end of the channel multiplier will successively strike the interior wall of the individual channels, knocking off secondary electrons to increase the number of output electrons relative to the number of input electrons.

However, it has been found 'that spurious outputs are produced by ion, in the case of an electron multiplier array, or photon feedback, these phenomena involving the feedback of ions or photons from the output end of the channel multiplier array to the area of the input end, the ion feedback producing a direct secondary multiplication effect and the photons causing the release of electrons from a photocathode surface. This feedback effect has been eliminated by several methods, one of which is described in copending application of Messrs. William Balas and Bagdasar Deradoorian, Ser. No. 772,527 filed Nov. 1, 1968 for Spiraled Channel Multiplier Assembly and Method of Assembly. In accordance with the disclosure of the aforementioned copending application, a plurality of individual channels are formed into a bundle and fed through a heating oven for drawing the channels to a particular size. During the drawing process, the bundle is given a twist by rotating either the feed or the pull apparatus under controlled conditions to impart a predetermined spiral to the bundle. Thus, the array is simultaneously sized and spiraled by means of a single machine.

However, in providing a bundle of channel multiplier elements in the form of an array, it has been found that the open area ratio or the ratio of the useful area to the total area available in the array may be substantially increased by the expansion of the walls of the elements within the confines of an outer tube. In accordance with the present invention, the bundle of individual channels may be formed as described in the copending application and the resultant spiraled array may be placed inside an outer glass tube, the tube being formed of a high temperature softening material relative to the material of the individual channels. Thus, when the assembly is heated, the outer jacket glass will soften at a temperature which is higher than the softening temperature of the individual channel multiplier elements.

In accordance with a preferred form of the present invention, a channel multiplier array is sealed at one end thereof and the other end remains open to the atmosphere. The interstitial space and the space between the array and the outer jacket is sealed at one end and the vacuum is drawn at the other end thereof. The entire assembly is then heated and the difference in pressure between atmosphere and the vacuum being drawn causes the walls of the channel multiplier bundle to move outwardly thus decreasing the wall thickness, filling the interstitial spaces and generally increasing the useful or open area of the array relative to the total area. In this way the collection efficiency of each individual channel multiplier element and the resultant array is greatly increased.

By use of the present invention, a spiraled channel multiplier array may be made cylindrical by fabricating a spiral array, inserting the array within a circular outer jacket and expanding the array to fill the interstitial spaces within the jacket. With a round exterior periphery, a plurality of the channel multiplier arrays may be bundled together to form an array assembly which is relatively compact, has a relatively high open area ratio and an increased efficiency.

Accordingly, it is one object of the present invention to provide an improved channel multiplier array.

It is another object of the present invention to provide an improved channel multiplier array wherein the individual channels are spiraled to eliminate feedback effects.

It is further object of the present invention to provide an improved channel multiplier array assembly, the assembly being made up ofa plurality of channel multiplier arrays.

It is still a further object of the present invention to increase the open area ratio or ratio of open area to total area in a channel multiplier array or a channel multiplier array assembly.

It is still another object of the present invention to improve channel multiplier arrays by decreasing the wall thickness of the individual channel while maintaining the total mechanical strength of the array.

It is still a further object of the present invention to provide an improved method of filling the interstitial spaces in a channel multiplier array.

Further objects, features and advantages of this invention will become apparent from a consideration of the following description, the appended claims and the accompanying drawing in which:

FIG. 1 is a schematic diagram illustrating a preferred method of forming a channel multiplier array in accordance with the present invention;

FIG. 2 is an end elevation illustrating a bundle of individual channel multipliers;

FIG. 3 is an end elevation illustrating the bundle of channel multipliers after it has been placed inside the high temperature softening glass tube;

FIG. 4 is a diagram schematically illustrating an apparatus for practicing the method of the present invention;

FIG. 5 is a sectional view illustrating the resultant channel multiplier array in cross section; and

FIG. 6 is an elevation view illustrating the side of the channel multiplier array of FIG. 5.

Referring now to the drawings, there is illustrated a preferred method of forming a multiplier array incorporating the features of the present invention. Particularly, a plurality of individual channel elements 10, which may number from two to several depending on the diameter of elements and the total diameter, are formed in a bundle 12 so that each individual channel element 10 is positioned within the bundle in the same relative position with respect to all of the other elements within the bundle at each point along the linear length of the channel elements. The bundle of channel elements is placed in an apparatus such as that described in conjunction with the above referenced copending application.

In accordance with the aforementioned application, the bundles are placed in a sizing and spiraling assembly whereby the bundle is inserted into and extends through an oven to heat the bundle and draw the elements to size. The feed por tion or the pull portion of the apparatus, as described in the aforementioned application, may be twisted to form a spiral in the bundle and eliminate ion or photon feedback from the multiplier assembly after it has been placed into use. After the bundle 12 has been formed and sized, it is placed in an outer jacket 14 of glass or other material as is illustrated in FIG. 3 of the drawings. It is to be noted that in FIGS. 2 and 3 a core 16 or cane has been placed in the interior portion of the individual bundles and the individual elements may be spiraled about the cane 16 in a manner known in the art. However, if the method of the copending application is utilized, the cane or support element may be eliminated, thus increasing the efficiency of the array.

The outer jacket 14 is formed of a higher temperature softening glass than the glass from which the elements 10 have been fabricated to permit the entire assembly to be heated to a temperature above that at which the bundle 12 will soften but below that at which the outerjacket 14 will soften.

The entire assembly, including bundle l2 and outer jacket 14 is placed in a heater 20 (FIG. 4) which may take the form of an electrical coil to heat the channel element assembly. However, prior to positioning the bundle in the heater 20, one end of the outer jacket 14 is sealed by some suitable method, for example by placing the ring 22 of temperature resistant material at one end thereof and surrounding the bundle 12. The ring 22 is to the outer jacket 14 and to the inner bundle l2, care being taken to preclude the sealing of the right end of bundle 12. The opposite end of the tube 14 is interconnected with a vacuum pump which is capable of evacuating the space between the bundle 12 and shell 14.

Further, the end of bundle 12 which is positioned between the seal 22 and the vacuum pump 24 is also sealed to preclude the evacuation of the volume within the inside diameter of the individual elements of the bundle 12. The other end of the bundle 12, the right end in the assembly illustrated, is left open to the atmosphere.

Upon completion of the assembly illustrated in FIG. 4, the vacuum pump is actuated to evacuate the volume described above and the heater assembly 20 is energized to soften the bundle 12. When the temperature reaches the softening point of the bundle 12, the pressure differential across the wall of the individual channel elements within bundle 12 will cause the elements to expand and fill the interstitial spaces between the elements of the bundle 12 and between the bundle 12 and the exterior jacket 14. The resultant channel multiplier array is illustrated in FIGS. and 6.

As is seen from FIG. 5, the walls of the individual elcmcnt have expanded outwardly to combine and fuse with the outer jacket 14 and form an integral mass therewith. Similarly, the interior walls have expanded to meet the interior walls of other elements and also have expanded to meet the cane element 16, in the situation where a cane is utilized, the spaces therebetween are completely filled. In this way a channel multiplier array has been formed which has a high ratio ofa useful area to total area at a cross section thereof, thus increasing the efficiency of the channel multiplier array. Also, the exterior surface of the array is cylindrical to facilitate assembling several arrays and increasing the overall efficiency of the final assembly.

While it will be apparent that the embodiments of the invention herein disclosed are will calculated to fulfill the objects of the invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

l. A channel multiplier array comprising a central core of a plurality of integrally formed individual channels fused together and having an interior electron emitting surface and fabricated of a first temperature softening material and an outer jacket surrounding said central core and fused thereto. fabricated of a second higher temperature softening material.

2. The improvement of claim 1 wherein said central core further includes a centrally disposed core fused to said plurality of fused individual channels. 

1. A channel multiplier array comprising A central core of a plurality of integrally formed individual channels fused together and having an interior electron emitting surface and fabricated of a first temperature softening material and an outer jacket surrounding said central core and fused thereto, fabricated of a second higher temperature softening material.
 2. The improvement of claim 1 wherein said central core further includes a centrally disposed core fused to said plurality of fused individual channels. 